P1.09-23 A33 and SATB2 Immunohistochemistry for Differentiating Metastatic Colorectal Carcinoma from Pulmonary Enteric Adenocarcinoma

Primary pulmonary enteric adenocarcinoma (PEAD) resemble morphology and immunohistochemistry with metastatic colorectal carcinoma(mCRC). it is sometimes difficult to differentiate PEAD from mCRC. Here, we evaluated the diagnostic value of A33 and SATB2 in discriminating between PEAD and mCRC. Resected 39 PEAD and 69 mCRC cases were retrospectively recruited. PEAD patients were performed colonoscopy postoperatively and were followed more than 1 year to exclude mCRC. Patients with mCRC were diagnosed by colorectal carcinoma history before or after thoracic surgery. A panel of immuohistochemistry markers were analyzed including A33, SATB2, CK7, CK20, TTF-1, Napisn A, CDX2 and villin. Tumor staining was scored for positive percentage and intensity, with a maximum possible score of 300. A33, SATB2 and CK20 showed specificity for PEAD: 94.9%, 92.3% and 88.9%, respectively; sensitivity for mCRC: 97.1%, 97.1% and 91.3%, respectively. CK7 expression was 91.4% sensitive and 90.9% specific for PEAD. A33 and SATB2 were slightly higher than CK20 for specificity in PEAD. The AUC for tumor staining of A33, SATB2 was 0.994 and 0.984, individually; In combination of them, the AUC was 1.000. The staining of TTF-1 was focal and weak in one mCRC case. No Napsin A expression was found in mCRC. The positive rate of TTF-1 and Naspin A expression in PEAD was 46.2% (18/39) and 25.6% (10/39). There was similar for CDX2 and villin expression between PEAD and mCRC. Our results showed that a panel of A33 and SATB2 was potentially optimal markers for differentiating PEAD from metastatic colorectal carcinoma.